Forest Ants Research Articles

Optimizing Diversity Assessment Protocols for High Canopy Ants in Tropical Rain Forest

ABSTRACTThe canopies of tropical rain forests support highly diverse, yet poorly known, animal and plant communities. It is vital that researchers who invest the time needed to gain access to the high canopy are able efficiently to survey the animals and plants that they find there. Here, we develop diversity assessment protocols for one of the most ecologically important canopy animal groups, the ants, in lowland dipterocarp rain forest in Sabah, Malaysia. We design and test a novel trap (the purse‐string trap) that can be remotely collected, thus avoiding disturbance to ants. We compare this modified trap with two other methods for surveying canopy ants: precision insecticide fogging and baited pitfall trapping. In total, we collected 39,351 ants belonging to 173 species in 38 genera. Fogging collected the most individuals and species, followed by purse‐string trapping with baited pitfall trapping catching the fewest. Fogging also resulted in samples with a different species composition to purse‐string trapping and baited pitfall trapping, which were not different from one another. Using a ‘greedy algorithm’, which guides the selection of inventory methods in order to maximize new species discovered per researcher‐hour, we show that projects allocating fewer than 132 researcher‐hours to canopy ant collection and identification should sample exclusively using fogging. Those with more time should use a combination of methods. This prioritization technique could be used to accelerate species discovery in future rapid biodiversity assessments.Abstract in Malay is available in the online version of this article.

Attendance and Co-Occurrence of Birds Following Army Ants in the Atlantic Rain Forest

In a first attempt to formally test competitive interactions among army-ant-following birds, we explored the patterns of occurrence of birds following swarms of army ants in the Atlantic rain forest of southeastern Brazil. We contrasted the frequency of occurrence of birds at ant swarms at a lowland and a highland site. Additionally, we assessed the patterns of co-occurrence of bird species at ant swarms, using null models to test for the possibility of competitive exclusion. Despite the larger number of attending bird species at the highland site, we detected no differences between the sites in either the frequency of attendance or the number of bird species per swarm. Analyses of co-occurrence did not reveal evidence of negative association of bird species attending ant swarms at the lowland site but did at the more species-rich highland site. Pairwise analyses showed that this negative association invariably involved two of the species attending ant swarms most frequently, Pyriglena leucoptera and Trichothraupis melanops, suggesting a competitive interaction. Possibly, although birds that are more dependent upon army ants avoid competitive exclusion by spatial segregation at the swarm's front, birds that follow army ants less frequently are occasionally excluded from the swarms.

Nine novel microsatellite markers for the army ant Simopelta pergandei (subfamily Ponerinae)

Simopelta (subfamily Ponerinae) army ants are specialized predators of other ants in New World tropical forests. Although they show a striking convergence in overall life-history with the well known army ants of the subfamilies Aenictinae, Dorylinae, and Ecitoninae, the genus has been little studied. We developed and characterized nine novel microsatellite loci for S. pergandei with 2–8 observed alleles (mean: 5.2) and expected heterozygosities between 0.16 and 0.87 (mean: 0.68). Three of these loci reliably cross-amplified in a second species, S. pentadentata, with 4–8 alleles (mean: 8.0) and expected heterozygosities between 0.32 and 0.85 (mean: 0.65). These genetic markers will be useful in studying the sociobiology and molecular ecology of Simopelta army ants and in elucidating convergent evolutionary trajectories that have culminated in the army ant lifestyle.

Nest density and distribution of subterranean ants in an evergreen broadleaf forest in Japan with special reference to Amblyopone silvestrii

AbstractThe density and distributions of nests of the subterranean ants were studied by excavation of thirty 1‐m2 quadrats in an evergreen broadleaf forest in central Japan. A total of 20 ant species were collected and the densities of Amblyopone silvestrii and Paratrechina flavipes were highest (both 0.83 nests/m2). The distribution patterns were analyzed by the Standardized Morisita Index (Ip) for the five species that had mean densities of more than 0.5 nests/m2. Of them, A. silvestrii and Hypoponera sauteri showed random distributions, while nests of Paratrechina flavipes were significantly overdispersed and those of Carebara yamatonis and Myrmecina nipponica were weakly clumped. These distributional patterns were discussed in connection with the ecology of the ants. In particular, the social organization of A. silvestrii was investigated based on the distributional pattern and the composition of collected colonies.

Is nest temperature an important factor for niche partitioning by leaf-litter ants (Hymenoptera: Formicidae) in Bornean rain forests?

Abstract:We tested the hypothesis that species of a diverse leaf-litter ant community are separated by the temperature preferences of their broods along a thermal gradient. Therefore, temperature preferences of brood-tending workers from 41 ant species co-occurring in four types (alluvial, limestone, kerangas and dipterocarp forest) of primary rain forest in Sarawak, Malaysia were measured in an experimental set-up. Preferred temperatures of species ranged from 16.0 °C to 31.7 °C, with the median at 25.8 °C. The ten commonest species (n ≥ 4) showed significantly different temperature preferences. In particular, species of the genus Pheidole differed clearly in their preferences over a broad range of temperatures. Temperature preferences varied significantly among ant assemblages from different forest types and nest sites. Experimentally obtained temperature preferences of species correlated significantly with vegetation density in the plots inhabited by the respective species, but not with plot canopy cover. When we tested the temperature preferences of all ant species with null models for niche overlap, we found a significant niche separation only among the tested species from the kerangas. Our results suggest that nest temperature is an important ecological factor for leaf-litter ants in rain forests on Borneo, but other factors may override its influence during community assembly.

The influence of nest availability on the abundance and diversity of twig-dwelling ants in a Papua New Guinea forest

Tropical ant communities are frequently diverse, but highly patchy in nature. The availability of suitable nest sites may be a regulating force in structuring litter ant communities. Our aim was to examine ant resource utilization in naturally occurring twigs, and to modify the availability of these resources in order to quantify the influence of nest availability on ant communities in a Papua New Guinean forest. First, we compared ant communities that assemble in artificial twigs (drilled, wooden dowels), naturally occurring twigs, and the leaf litter. A total of 55 ant species were captured: 33 from the leaf litter, 29 from naturally occurring twigs, and only 12 from artificial nests. Significantly different communities formed in each of the three nest types. Second, we examined how the density of natural or artificial nest material influenced the ant abundance and species richness. Plots had between 5 and 96 potential nest sites. An average of only 11.2% of these twigs was colonized. Both species richness and the total abundance of adult ants were significantly positively correlated with increasing naturally occurring twig density. Conversely, increasing the availability of artificial nests from 5 to 20 per plot had no significant effect on the proportion of artificial nests colonized, species richness, or the colony size. We observed that ant species richness and abundance increased with natural twig density, at least for naturally occurring communities. But why so many twigs remain vacant and available for ant colonization remains unknown. Other biotic and abiotic factors likely influence the use of nesting habitat in these ant communities.

Effectiveness and Biases of Winkler Litter Extraction and Pitfall Trapping for Collecting Ground-Dwelling Ants in Northern Temperate Forests

The sampling efficiency of pitfall traps and Winkler litter extraction in northern deciduous forests was compared using ants. Both techniques are among the most common methods used to measure the diversity of organisms active on the forest floor. During 2005-2006, 90 Winkler and 180 pitfall trap samples from urban forest fragments in northeastern Ohio obtained 9,203 ants representing 31 species. Winklers captured all 31 species, whereas pitfall traps collected a total of 24 species. Winkler samples accumulated species more rapidly than did pitfall traps and had greater total species richness and higher abundance of ants recorded. Consistent with other studies, Winkler sampling was found to catch a greater number of smaller ants, whereas pitfall trapping caught a greater number of large-bodied ants. According to estimates of expected species richness, the combination of the two sampling techniques allowed for the collection of approximately 90% of the ants expected in the surveyed area. Site variation had little effect on the inherent differences in sampling efficacy between the two methods. Either technique adequately collected samples for broad comparisons and documentation of the more typical and representative ant fauna, but Winkler extraction exhibited the advantage of a more complete inventory. The application of both techniques should be considered if the aims of a study require estimation of community properties, such as relative abundance.

Utilização de sementes de Syagrus romanzoffiana (Arecaceae) por formigas em floresta secundária no Sul do Brasil

Ants can nest in a wide variety of substracts. This paper shows Syagrus romanzoffiana seed utilization by ants in an Atlantic secondary forest. We report 29 seeds occupied by small-bodied ants, with 27 of them showing at least two ant development stages. Although a large number of seeds were sampled, a low level of ant occupation was observed.

Carbohydrate supply limits invasion of natural communities by Argentine ants

The ability of species to invade new habitats is often limited by various biotic and physical factors or interactions between the two. Invasive ants, frequently associated with human activities, flourish in disturbed urban and agricultural environments. However, their ability to invade and establish in natural habitats is more variable. This is particularly so for the invasive Argentine ant (Linepithema humile). While biotic resistance and low soil moisture limits their invasion of natural habitats in some instances, the effect of food availability has been poorly explored. We conducted field experiments to determine if resource availability limits the spread and persistence of Argentine ants in remnant natural forest in North Carolina. Replicated transects paired with and without sucrose solution feeding stations were run from invaded urban edges into forest remnants and compared over time using baits and direct counts at feeding stations. Repeated under different timing regimes in 2006 and 2007, access to sucrose increased local Argentine ant abundances (1.6-2.5 fold) and facilitated their progression into the forest up to 73 +/- 21% of 50-m transects. Resource removal caused an expected decrease in Argentine ant densities in 2006, in conjunction with their retreat to the urban/forest boundary. However, in 2007, Argentine ant numbers unexpectedly continued to increase in the absence of sugar stations, possibly through access to alternative resources or conditions not available the previous year such as honeydew-excreting Hemiptera. Our results showed that supplementing carbohydrate supply facilitates invasion of natural habitat by Argentine ants. This is particularly evident where Argentine ants continued to thrive following sugar station removal.

Ant community responses to experimental fire and logging in a eucalypt forest of south-eastern Australia

Sustainable forest management requires a sound understanding of the impacts of forestry management practices, especially prescribed fire and timber harvesting, on biodiversity. Many studies have examined the impacts of fire and logging separately, but few have considered them together. Here we describe the combined effects of selective logging and repeated prescribed fire on ants in eucalypt forest near Eden in south-eastern Australia. The study was conducted within 18 experimental coupes comprising three replicates of each of six treatments, representing combinations of two logging (selectively logged and unlogged) and three prescribed burning (unburnt, routine and high fire frequency over 20 years) practices. Ants were sampled using terrestrial and arboreal pitfall traps in two plots within each of the 18 coupes. A total of 92 species from 35 genera were recorded, with ant species richness increasing with both increasing fire frequency and selective harvesting. We also found significant differences in ant species composition between management treatments; however, these differences were rather modest, and apparent only between extremes of fire and harvesting combinations. Logging on its own was not a significant factor contributing to variation in ant species composition. However, the responses of two common species and a key functional group to fire depended on logging treatment; in each case their abundance decreased with increasing fire frequency at unlogged sites, but increased at logged sites. The general resilience of ant communities suggests that forests remain in good functional health even when subject to a combination of selective logging and frequent burning. However, our study under-sampled species with specialist microhabitat requirements, and these might have been more heavily impacted. We have also revealed some significant interactions between the effects of fire and logging, which highlights the importance of considering combined impacts of forest management practices.

Sampling for ants in different-aged spruce forests: A comparison of methods

It is necessary to use special sampling method for studying of each animal group. However each method has its specificity and describes the studied community a bit differently. Three common methods for sampling of ants were compared: soil excavation, pitfall traps and baits. Ants were sampled in 25 patches in a large spruce forest in the Czech Republic during 2005 and 2006. Each patch represented one of five age classes (0–2, 3–5, 8–12, 26–41 and 85–105 years old), and the patches were located in five sites such that the five patches in each site formed a chronosequence. The percentage of variability in ants as explained by other sampling techniques was as follows: 60.0% of the variability in bait data was explained by pitfall trap data, while only 19.7% of the variability in pitfall trap data was explained by excavation data. Species and numbers of ants on baits were strongly affected by bait type: Myrmica species preferred honey whereas Formicinae preferred tuna bait. Assembly composition in pitfall traps varied significantly between study sites. The position of sampling site in landscape (location in the forest regardless of the immediate habitat type where the trap was located) hence strongly affected ants. Proportions of ants in particular methods were equal in the majority of cases. For excavation samples, ant numbers and species were more influenced by the immediate habitat than the wider habitat, but the opposite was true for samples from pitfall traps.

Temporal patterns of nutrient availability around nests of leaf-cutting ants ( Atta colombica) in secondary moist tropical forest

Leaf-cutting ants consume up to 10% of canopy leaves in the foraging area of their colony and therefore represent a key perturbation in the nutrient cycle of tropical forests. We used a chronosequence of nest sites on Barro Colorado Island, Panama, to assess the influence of leaf-cutting ants ( Atta colombica) on nutrient availability in a neotropical rainforest. Twelve nest sites were sampled, including active nests, recently abandoned nests (<1 year) and long-abandoned nests (>1 year). Waste material discarded by the ants down-slope from the nests contained large concentrations of nitrogen and phosphorus in both total and soluble forms, but decomposed within one year after the nests were abandoned. Despite this, soil under the waste material contained high concentrations of nitrate and ammonium that persisted after the disappearance of the waste, although soluble phosphate returned to background concentrations within one year of nest abandonment. Fine roots were more abundant in soil under waste than control soils up to one year after nest abandonment, but were not significantly different for older sites. In contrast to the waste dumps, soil above the underground nest chambers consistently contained lower nutrient concentrations than control soils, although this was not statistically significant. We conclude that the ‘islands of fertility’ created by leaf-cutting ants provide a nutritional benefit to nearby plants for less than one year after nest abandonment in the moist tropical environment of Barro Colorado Island.

Fuelling the biodiversity crisis: species loss of ground-dwelling forest ants in oil palm plantations in Sabah, Malaysia (Borneo)

Oil palm plantations today cover large areas of former tropical lowland rain forest in Southeast Asia and are rapidly expanding on the island of Borneo. Study of the community of ground-dwelling ants in different plantations in Sabah, Malaysia, over 2 years using tuna baiting, revealed that the oil palm plantation ground ant community was severely reduced in species richness in comparison to the forest interior, regardless of age, undergrowth cover, or proximity to neighbouring forest. The results indicate that oil palm plantation habitats, now covering more than 15% of Sabah’s land area, can sustain only about 5% of the ground-dwelling ant species of the forest interior. Nine of the 23 ant species baited in the plantations were never recorded inside forest. All numerically dominant ants were non-forest species. The most common species was Anoplolepis gracilipes, an invasive species present at 70% of all bait sites and known to cause ‘ecological meltdowns’ in other situations. The low frequency and species number of forest ground ants indicates that oil palm plantations act as effective dispersal barriers leading to community isolation in rain forest remnants. The replacement of natural forests with oil palm plantations poses a serious threat to the conservation of biodiversity on Borneo if similar results are confirmed in other taxa.

Hormigas: relaciones especies-área en fragmentos de bosque seco tropical

We analyzed the effect of fragmentation on ant species-area and specimen frequency-area relationships in nine patches of tropical dry forest in the middle Cauca river basin in Colombia. Species richness and specimen relative frequency of ants were positively correlated with area, whereas no significant correlation was found between species richness and the degree of isolation calculated for the forest patches. As the fragmentation affects different functional groups in different ways, we analyzed the species-area relationship for separate functional groups of ants. According to the habitat requirements we found that the species richness increased faster as area increased for ants inhabiting decomposing wood, followed by ants associated with trees, while species richness of ants living under dead leaves did not correlate with area. According to the food preference, species richness was positively correlated with area for the army ant group, while no significant correlation was found for solitary hunters or for leaf-cutting ants. Ant species richness and specimen density were calculated from equal size samples and examined in relation to the habitat area. An inverse correlation was found only for specimen density, the opposite of what was expected. To our knowledge this is one of the first studies showing differential responses of functional groups of ants to habitat loss. Moreover, it emphasizes the conservation value of small forest fragments for ants in a tropical dry forest.

Breeding system, colony and population structure in the weaver antOecophylla smaragdina

Weaver ants (Oecophylla smaragdina) are dominant ants in open forests from India, Australia, China and Southeast Asia, whose leaf nests are held together with larval silk. The species, together with its sole congener O. longinoda, has been important in research on biological control, communication, territoriality and colony integration. Over most of the range, only one queen has been found per colony, but the occurrence of several queens per nest has been reported for the Australian Northern Territory. The number of males mating with each queen is little known. Here we report on the colony structure of O. smaragdina using published and new microsatellite markers. Worker genotype arrays reflect the occurrence of habitual polygyny (more than one queen per colony) in 18 colonies from Darwin, Northern Australia, with up to five queens inferred per colony. Monogyny (one queen per colony) with occasional polygyny was inferred for 14 colonies from Queensland, Australia, and 20 colonies from Java, Indonesia. Direct genotyping of the sperm carried by 77 Queensland queens and worker genotypic arrays of established colonies yielded similar results, indicating that less than half of the queens mate only once and some mate up to five times. Worker genotype arrays indicated that queens from Java and the Northern Territory also often mate with more than one male, but less often than those from Queensland. A strong isolation-by-distance effect was found for Queensland samples. The variation uncovered means that O. smaragdina is a more versatile study system than previously supposed.

Edge‐mediated reduction of phorid parasitism on leaf‐cutting ants in a Brazilian Atlantic forest

AbstractPrevious studies have shown that leaf‐cutting ant populations benefit greatly from living in or near the edges of the Brazilian Atlantic forest. One of the mechanisms responsible for this rise in population density is an edge‐mediated increase of pioneer plants, resulting in increased food availability for the ants (i.e., less bottom‐up control). Here, we hypothesized that the release from natural enemies (i.e., less top‐down control) may also contribute to the phenomenon. We investigated whether parasitism of phorid flies on leaf‐cutting ants decreases in colonies located along the forest edge vs. the interior of a large tract of Atlantic forest in northeastern Brazil. For this, we assessed abundance and rates of oviposition attack by phorids in bimonthly intervals over a period of 1 year in 10 adult colonies of Atta cephalotes (L.) (Hymenoptera: Formicidae: Myrmicinae), five at the forest edge and five in the forest interior. The number of phorids attracted by ants at edge colonies was 40% lower than that at interior colonies. The temporal variation in phorid attraction was also significant, with approximately 35% fewer flies in the dry months as compared to the rainy months. As a result of lower phorid abundance, ant workers of edge colonies suffered three times fewer oviposition attacks than those of interior colonies. There was a tendency for fewer attacks during dry months, but the difference in the temporal variation was not significant. Our findings suggest that edge creation contributes to increased leaf‐cutting ant abundance, not only via the attenuation of bottom‐up forces, but also through an environmentally triggered depression of parasitoid abundance/efficiency, possibly because of adverse environmental conditions in edge habitats.

Ecological Partitioning and Invasive Ants (Hymenoptera: Formicidae) in a Tropical Rain Forest Ant Community from Fiji1

Determining composition and structure of ant communities may help understand how niche opportunities become available for invasive ant species and ultimately how communities are invaded. This study examined composition and structure of an ant community from a tropical rain forest in Fiji, specifically looking at spatial partitioning and presence of invasive ant species. A total of 27 species was collected, including five invasive species. Spatial partitioning between arboreal (foliage beating) and litter (quadrat) samples was evident with a relatively low species overlap and a different composition of ant genera. Composition and abundance of ants was also significantly different between litter and arboreal microhabitats at baits, but not at different bait types (oil, sugar, tuna). In terms of invasive ant species, there was no difference in number of invasive species between canopy and litter. However, the most common species, Paratrechina vaga, was significantly less abundant and less frequently collected in the canopy. In arboreal samples, invasive species were significantly smaller than endemic species, which may have provided an opportunity for invasive species to become established. However, taxonomic disharmony (missing elements in the fauna) could also play an important role in success of invasive ant species across the Pacific region. Invasive ants represent a serious threat to biodiversity in Fiji and on many other Pacific islands. A greater understanding of habitat susceptibility and mechanisms for invasion may help mitigate their impacts.

Biodiversity Loss in Latin American Coffee Landscapes: Review of the Evidence on Ants, Birds, and Trees

Studies have documented biodiversity losses due to intensification of coffee management (reduction in canopy richness and complexity). Nevertheless, questions remain regarding relative sensitivity of different taxa, habitat specialists, and functional groups, and whether implications for biodiversity conservation vary across regions.We quantitatively reviewed data from ant, bird, and tree biodiversity studies in coffee agroecosystems to address the following questions: Does species richness decline with intensification or with individual vegetation characteristics? Are there significant losses of species richness in coffee-management systems compared with forests? Is species loss greater for forest species or for particular functional groups?and Are ants or birds more strongly affected by intensification? Across studies, ant and bird richness declined with management intensification and with changes in vegetation. Species richness of all ants and birds and of forest ant and bird species was lower in most coffee agroecosystems than in forests, but rustic coffee (grown under native forest canopies) had equal or greater ant and bird richness than nearby forests. Sun coffee(grown without canopy trees) sustained the highest species losses, and species loss of forest ant, bird, and tree species increased with management intensity. Losses of ant and bird species were similar, although losses of forest ants were more drastic in rustic coffee. Richness of migratory birds and of birds that forage across vegetation strata was less affected by intensification than richness of resident, canopy, and understory bird species. Rustic farms protected more species than other coffee systems, and loss of species depended greatly on habitat specialization and functional traits. We recommend that forest be protected, rustic coffee be promoted,and intensive coffee farms be restored by augmenting native tree density and richness and allowing growth of epiphytes. We also recommend that future research focus on potential trade-offs between biodiversity conservation and farmer livelihoods stemming from coffee production.

Difference in seasonal activity pattern between non‐native and native ants in subtropical forest of Okinawa Island, Japan

AbstractBiological invasions by non‐native tramp ants are reported throughout the world, particularly in island ecosystems. In Okinawa Island, a subtropical island in south‐western Japan, many tramp ants including the invasive ant, Anoplolepis gracilipes, already occur. In this study activity patterns of the ground‐foraging tramp and native ants were investigated for one year by using food bait traps at the forest edges where both categories of ants coexist. On a seasonal time scale, activity patterns were different between exotic and native ants. Native ants are active and seemingly more dominant from spring to summer whereas tramp ants become more dominant from autumn to winter. These results suggest there might be temporal niche partitioning between tramp and native ants, and native ants might be able to dominate tramp ants in their suitable seasons.

Gas permeable deep reaching fracture zones encourage site selection of ants

Abstract Difficulties with geological mapping of fault patterns occur frequently due to missing outcrops and typically fault mineralization (e.g. crystalline quartz and ore mineralization). Alternatively, in addition to other analyses, soil gas measurements (e.g. helium) can be carried out. Due to fault zone complexity, geologists must often rely on other, in some cases, easier indications of their existence. Geological studies in several areas of central Europe especially in the Middle Rhine Region (Rhenish Massif) indicate that active gas permeable fracture zones are linked to linear distributions of nests of hill-building forest ants. Therefore, the possibility of using formicines as indicators of gas permeable fault patterns was investigated. These preliminary data indicated the possible interaction of site selection and active gas permeable fracture zones. Consequently, regions in the Alps, the Black Forest, the Lower Rhine Embayment, Bavaria, Hesse and South Sweden were chosen, ant nests were mapped, and their sites subsequently compared to geological structures. Most of the investigated ant nests were located on or near active gas permeable faults. Additionally, in the Middle Rhine Region variations in population size of formicines on fault zones and inter fault zones have been observed. These primary data suggest formicines can be applied successfully as an aid to fault pattern location.